1. Field of the Invention
The present invention relates to a pushing device used for, for example, bonding machines to feed out plate-form parts.
2. Prior Art
Generally, plate-form parts such as lead frames are stored in a storage magazine in a stacked manner. When work, such as bonding, is performed on such lead frames, it is necessary to feed out the lead frames from the magazine one at a time to a predetermined position on feeder rails.
This feed-out operation is usually accomplished in a following manner: Each lead frame is fed out by a fixed amount onto the feeder rails from the storage magazine by a pusher of a pushing device. Alternately, each lead frame can individually be picked up from the magazine by a separating apparatus and placed on the feeder rails. After the lead frame is placed on the feeder rails, it is pushed a fixed distance by the pusher of the pushing device and transported to a working area by a conveying means.
Some conventional pushing devices use air cylinders as a driving source for the pusher. One example of this type of device is described in the Japanese Patent Application Laid-Open ("Kokai") No. 54-87475.
In this prior art, the pusher is driven a fixed distance by air cylinders. Thus, when the type of lead frame to be handled is changed (and more specifically if the length of the lead frame changes), it is, in order to insure the lead frames to be fed out to a prescribed position on the feeder rails, necessary either to change the pusher to another type of pusher or change the position of the pushing device. However, such change-over work requires considerable time and skill. Also, it could result in poor productivity.